The present invention relates to a vehicular signal lamp, particularly to the composition of a reflector surface or lens of a vehicular signal lamp.
In general, vehicular signal lamps irradiate a light beam in the forward direction of the lamp with a certain amount of extension in both right and left directions in order to allow the light signal to be recognized when the lamp is viewed not only directly from in front of the lamp but also from right and left lateral directions.
For this purpose, there is known a lamp as shown in FIG. 12A constructed to diffuse and reflect the light from a light source bulb 2, reflected as a substantially parallel light beam by a reflecting surface 4a of a reflector 4, in right and left directions by a plurality of lens elements 6s formed on a front lens 6, and also a lamp as shown in FIG. 12B constructed to diffuse and reflect the light from the light source bulb 2 in right and left directions by a plurality of reflecting elements 4s formed on the reflecting surface 4a of the reflector.
However, in the conventional vehicular signal lamp there occur problems, as described below, due to the fact that the right and left maximum diffusion angles xcex8L and xcex8R of the transmitted light from respective lens elements 6s or the reflected light from respective reflecting elements 4s are the same among all the lens elements 6s or among all the reflecting elements 4s. 
For example, in a vehicular signal lamp as shown in FIG. 12B, suppose the light is observed in a lateral direction by moving the viewing position from the front direction gradually to the right. (As used herein, xe2x80x9crightxe2x80x9d and xe2x80x9cleftxe2x80x9d refer to directions taken with respect to the light front direction, i.e., the direction of the main beam from the lamp).
As shown in FIG. 13 and FIG. 14, when the viewing position is moved somewhat from the light front direction to the right, concerning a reflecting element 4s(1) positioned at the right side of the reflecting surface 4a, at a viewing position E the viewing angle for the reflecting element 4s(1) (angle for looking at the reflecting element 4s from the viewing position) xcex1R is smaller than the right direction maximum diffusion angle xcex8R of the same element, and, on the other hand, concerning a reflecting element 4s(2) positioned at the left side of the reflecting surface 4a, the element viewing angle xcex1R is larger than the right direction maximum diffusion angle xcex8L thereof.
Thus, at the viewing position E the reflecting element 4s(1) on the right side appears brighter than the reflecting element 4s(2) on the left side because reflected light from the former element reaches the viewing position E, while the reflecting element 4s(2) on the left end side appears dark because there is no reflected light directed to the viewing position E. Consequently, as shown in FIG. 15, the reflecting area on the right side of the reflecting surface appears bright, but the reflecting area on the left side of the reflecting surface appears dark. In FIG. 15, black band portions Br extending in vertical stripes in the area in the vicinity of the right end portion of respective reflecting elements 4s correspond to the brightly appearing portions of the reflecting elements 4s. 
Such a phenomenon occurs similarly in the case where the viewing position is moved from the front direction to the left, and also similarly for a vehicular signal lamp as shown in FIG. 12A.
The occurrence of such phenomenon, wherein the reflecting surface or lens that appears universally bright when viewed from a position directly in front of the lamp has portions that appear dark when the viewing position is moved to the right or left direction, impairs the overall appearance of the lamp, and is undesirable in respect of appearance quality in a vehicular signal lamp.
It is of course possible to make the lamp appear bright over a certain angular viewing position range by increasing the light maximum diffusion angle. However, if the maximum diffusion angle is simply increased, the light is diffused into unnecessary areas, the middle portion becomes dark, or the lamp must be undesirably increased in size.
The present invention was conceived in view of such problems, and it is an object of the invention to provide a vehicular signal lamp providing a good appearance even when the lamp is observed from a lateral direction where the viewing position is moved to the right or left from the front direction.
The invention achieves the above object by appropriately constructing the respective reflecting elements composing the reflecting surface of the reflector or the respective lens elements formed on the front lens.
In accordance with a first embodiment of the present invention a signal lamp is provided which comprises a light source bulb, a reflector for reflecting forward the light from the light source bulb, and a front lens provided at the forward side of the reflector, wherein the reflecting surface of the reflector comprises a plurality of reflecting elements for diffusing and reflecting in right and left directions the light from the light source bulb, and the front lens is transparent and is characterized in that the maximum diffusion angle in at least one of right and left directions of the reflected light from the respective reflecting elements is set to a smaller value the nearer the reflecting element is located to the end of the one side in the reflecting surface.
To make the maximum diffusion angle in at least one of the right and left directions smaller the nearer the reflecting element is located to the end of the one side of the reflecting surface, the left direction maximum diffusion angle may be set to a smaller value the nearer the reflecting element is located to the left end of the reflecting surface, the right direction maximum diffusion angle may be set to a smaller value the nearer the reflecting element is located to the right end of the reflecting surface, or the left direction maximum diffusion angle may be set to a smaller value the nearer the reflecting element is located to the left end of the reflecting surface, and the right direction maximum diffusion angle is set to a smaller value the nearer the reflecting element is located to the right end of the reflecting surface.
A second embodiment of a signal lamp of the present invention comprises a light source bulb, a reflector for reflecting forward the light from the light source bulb, and a front lens provided at the forward side of the reflector, the reflecting surface of the reflector being constructed to reflect the light from the light source bulb as a substantially parallel light beam, and a plurality of lens elements for diffusing and transmitting in right and left directions the reflected light from the reflecting surface are formed on the front lens, wherein the maximum diffusion angle in at least one of right and left directions of the transmitted light from the respective lens elements is set to a smaller value the nearer the lens element is located to the end of the one side of the front lens.
To make the maximum diffusion angle in at least one of right and left directions smaller the nearer the lens element is located to the end of the one side in the lens, the left direction maximum diffusion angle may be set to a smaller value the nearer the lens element is located to the left end of the lens, the right direction maximum diffusion angle may set to a smaller value the nearer the lens element is located to the right end of the lens, or the left direction maximum diffusion angle may be set to a smaller value the nearer the lens element is located to the left end of the lens, and the right direction maximum diffusion angle is set to a smaller value the nearer the lens element is located to the right end of the lens.
In both embodiments, the specific value of the maximum diffusion angle is not particularly limited, but it may be conveniently set to a value within a desirable angular range, for example, within a range of approximately 20 to 40 degrees with respect to the front direction.
Moreover, the arrangement of the plurality of reflecting elements and the plurality of lens elements is not particularly limited, and arrangements wherein the various elements are divided and arranged in vertical stripes or in a lattice or the like can be adopted. In addition, the various reflecting elements or lens elements may or may not have a vertical direction diffusing function, although they must necessarily have a right and left direction diffusion function.
The vehicular signal lamp according to the first embodiment of the present invention, which comprises a plurality of reflecting elements formed on the reflecting surface of the reflector for diffusing and reflecting in right and left directions the light from the light source bulb, and in which the maximum diffusion angle in at least one of right and left directions is set to a smaller value the nearer the reflecting element is to the end of the one side on the reflecting surface, provides the following operational advantages.
When the light is observed in a lateral direction by moving the viewing position from the light front direction to the right or left, the entire reflecting surface looks bright within a certain light viewing angle, rather than the bright portion of the reflecting area decreasing as the light viewing angle increases, as in the conventional lamp.
Consequently, with the signal lamp constructed in accordance with the first embodiment of the invention a good illuminating appearance is obtained even when the lamp is observed from a lateral direction, moving the viewing position to the right or left from the light front direction.
In this case, the reflecting surface can be formed without creating graduations or ridge lines by arranging concave horizontal section reflecting elements and convex horizontal section reflecting elements alternatingly in the right and left directions, thereby further improving the appearance of the lamp.
On the other hand, in the vehicular signal lamp according to the second embodiment of the invention, the reflecting surface of the reflector is formed to reflect the light from the light source bulb as a substantially parallel light beam, and a plurality of lens elements for diffusing and transmitting in right and left directions the reflected light from the reflecting surface are formed on the front lens. With this arrangement, the following operational advantages are obtained because the maximum diffusion angle in at least one of right and left directions of the transmitted light from the respective lens elements is set to a smaller value the nearer the lens element is located to the end of the one side on the lens.
When the light is observed in a lateral direction by moving the viewing position from the light front direction to the right or left, the entire reflecting surface appears bright through a certain light viewing angle, rather than the bright portions of the lens area decreasing as the light viewing angle increases, as in the conventional lamp.
Consequently, according to the second embodiment of the invention a good appearance is obtained even when the light is observed from a lateral direction, moving the viewing position to the right or left from the light front direction.
In either embodiment, the specific configuration of the plurality of reflecting elements and the plurality of lens elements are not particularly limited as mentioned above, and the following operational advantages can be obtained by arranging the reflecting or lens elements so that the reflected light from the respective reflecting elements or the transmitted light from the respective lens elements in the direction of the maximum diffusion angle substantially converge at a position 3 to 5 m forward of the lamp.
That is, in actual vehicle operating situations the vehicular signal lamp is observed by drivers of following vehicles, vehicles that the vehicle is passing, or the like from a position 3 to 5 m or so away from the lamp even in the closest case. Therefore, a phenomenon wherein the entire reflecting surface appears bright within a certain light viewing angle under actual vehicle operating conditions can be obtained by substantially converging the reflected light from the respective reflecting elements or the transmitted light from the respective lens elements in the direction of the maximum diffusion angle at a position 3 to 5 m forward of the lamp.
Many vehicular signal lamps are paired and disposed in right and left directions of the vehicle with a predetermined interval therebetween. In each embodiment the appearance of the two lamps can be harmonized when both lamps are observed while moving the viewing position in the right and left directions by setting the maximum diffusion angle toward the one side of the reflected light from the respective lens elements or the transmitted light from the respective reflecting elements to a value smaller than the vehicular signal lamp of the other side.